The cell cycle defines an orderly series of events that together make up the process of cell duplication. Research over the past thirty years has confirmed that most of the fundamental cell cycle events are conserved across all eukaryotic lineages. We have undertaken a genetic analysis of cell cycle events in yeast under the assumption that findings made using this simple genetically tractable organism will be of general interest and utility. The experiments proposed are aimed at elucidating the molecular basis for cell cycle progression and control in three general areas: (1) regulation of the cell cycle by proteolysis of key regulatory proteins; (2) regulation of mitotic spindle development; and (3) cell cycle regulation of cellular morphogenesis. In each case, a strategy of combiningmolecular and genetic approaches, that has proved extremely successful with yeast, is planned. It is anticipatedthat the proposed research will synergize with work in other experimental systems, and thus contribute to the general elucidation of the molecular basis for cell cycle progression and control. Ultimately, such information will be important for the diagnosis and treatment of human diseases such as cancer.